The epidemiology of genital chlamydial infection in South Australia.

All laboratory tests performed and medical reports received in South Australia in 1990-1991 and screening results for Chlamydia trachomatis at the central STD clinic from 1988-1991 were analysed to clarify the epidemiology of genital chlamydial infection. From 70,494 laboratory tests in 1990-1991, 2449 (3.5%) infections were detected of which 2431 (99%) were also reported by clinicians. Infections were detected in 1335 (6.4%) of 21,004 patients (71% of 29,401 attendees) screened at the central STD clinic from 1988 to 1991. STD clinic yields suggest a male:female ratio of 1.08:1 (95% confidence intervals = 1.05:1-1.11:1), with 46% of infections in males and 67% of infections in females being asymptomatic. For both males and females, infection rates were highest in 15-19-year-olds and decreased with increasing age, but were not independently related to marital status. The statewide epidemiological pattern was probably distorted in medical reports because of selection biases in testing (89% of tests performed by non-STD clinicians were on females) which resulted in decreased detection in asymptomatic females, symptomatic and asymptomatic males, married persons and unmarried young persons 15-19-year-old females and 15-24-year-old males) by private practitioners. A cost-effective method for increased detection of chlamydial infection in undertested groups (particularly of asymptomatic unmarried males aged 15-24) will be required to control transmission of chlamydial infection in South Australia. Increased detection in young married persons is also desirable.